Hello, we realized, that multiple ping floods (ping -f) can cause very large high-priority process latencies (up to a many seconds) on a MPC5200 PowerPC system with FEC NAPI support. The latencies are measured with
# cyclictest -p 80 -n The problem is that processing of the ICMP pakets in the Hard-Irq and Soft-IRQ context can last for a long time without returning to the scheduler. Reducing MAX_SOFTIRQ_RESTART from 10 to 2 helps - the latency goes down to 35 ms with 2 "ping -f" - but it's not a configurable parameter, even if it somehow depends on the CPU power. And using the -rt patches seems overkill to me. Any other ideas or comments on how to get rid of such high process latencies? Wolfgang. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
